where does water in modern plumbing come from and where does it go?

Question

I don’t understand how you can just leave the tap on–where does that water come from?

Is the water from your kitchen sink and your toilet the same water?

Is water really being “wasted”?

In: Engineering

Answer 1

Water is not “wasted” in the sense that it ceases to be. However, the water that comes from your supply lines is clean water that is safe to drink, bathe in, etc. (even if you use it to fill the toilet or water the lawn.)

For a major city utility, the water usually comes from large surface bodies of water such as lakes or rivers. This water (usually basically clean, if not literally safe to drink) is pumped to a treatment station, and goes through the appropriate processes to meet the stringent standards to be considered “potable”. It is then pumped, at pressure, to consumers of the water. (It is important the pressure remain at a certain level, or mud surrounding the pipes can infiltrate the water supply.)

Once it comes out of your faucet, it cannot be re-used until it has been treated to remove whatever contaminants might have been introduced. If you are on a city utility, this will generally be via a “sanitary sewer” system, where the waste will work its way to a treatment plant, where the miracle of modern sanitation engineering will at least render it safe enough to introduce back into surface or ground waters without harming the ecosystem. The eventual output of the treatment plant may go into a body of water that has an intake some distance downstream. (In rare cases, the output of sewage treatment goes right into the freshwater intake, but this is rare.)

When you run your faucet, the meter is measuring how much water you use, and then you are billed for both the costs to make the water safe to drink, and usually also the costs to make your sewage safe for the environment.